Sound reproducing means and method



y 1933. R. T. FRIEBUS SOUND REPRODUCING MEANS AND METHOD Filed May 21, 1929 INVENTOR REGINALD T. FRIEBUS ATTORNEY Patented July 4, 1933 UNlTED REGINALD 'l. FRIEBUS, OF lvIONTCLAIR, NEH? JEE 'EY, ASSIGKYOE '16 GULUI'JIBIA. PHDITQ- GRAPH COMPANY, ENG, 0F BBIDG'EPORT, CQHNECTICUT, A OSHEORMJEEQTJ 05 NEW YORK SOUND REIBODUCING Application filed May 21,

This invention relates to new and useful improvements in method and means of reproducing sound.

An object of the invention is to provide method of reproducing sound wherein the object bearing the recorded sound is not of reproducing sound from a disc phonograph record consisting in casting a light beam on the record and intercepting reflected light rays and converting them into sound.

A still further object of the invention is to provide a means for carrying out the foregoing objects.

Yet another object is to provide a means and method for the purpose indicated, which means and method is adapted to reproduce sound from a wax master; from a metallic electroplate of the wax master (he the electroplate either positive or negative), whose surface is polished or covered with mercury or some other plating capable of taking high polish such as silver, gold, nickle or uranium, or from the ordinary commercial disc phonograph record.

Other objects and advantages will become apparent from the following detailed. description taken in connection with the accompanying drawing, wherein in a. more or less diagrammatic manner is illustrated an embodiment of the invention.

mg a single record groove and also diagrammatically showing the llght beam entering MEANS AND METHOD 1929. Serial No. 364,897.

the groove and reflected by the side wall thereof; and

Fig. 3 is a plan view of a section of the record greatly enlarged and illustrating the manner in which the wall of a groove is il luminated.

By the present disclosure, the invention is shown as applied to the reproduction of sound from an ordinary commercial phonograph record. However, it will he understood that the invention has other applications and that the present disclosure is for the purpose of illustration only and that reference must be had to the claims for a delinition of the limitations oi th invention.

In the following description and in the claims, the words sound record or the word record is used to indicate any object carrying a recording of sound. Record disc or phonograph record is used to any phonograph record or any disc shaped record be it made as is the ordinary com1nercia-l phonograph record, or be it a wax mas ter or an electroplate oil the latter.

Referring in detail to the drawin at 5 shown a phonograph turn table, carried by a spindle 6 adapted to be rotated hy any suitable means (not shown), and mounted on the turn table 5 is an ordinary disc phonograph record 7. cording to the present invention, a stca y light is emitted iii-om a source 8 and directed into and along the grooves of the record 7.

This steady light is reflected by the sn'iooth inclined wall of the record groove, as indi cated by the line 9 into a microscope 10. Due to the curvature of the wall of groove and the undulations in the wall, th reflected light is intermittent or flickering. The intermittent or flickering light passed through. the microscope 10 and falls upon a light sensitive cell such as a photo-electric cell ll enclosed within a casing 12 disposed over the end or eye-piece of the microscope 10.

Since the photo-electric cell 11 is disposed.

11 to a suitable amplifying arrangement indicated at 13, and thence through wires 14; to a. lound speaker 15 which transforms the electrical impulses into sound.

Figs. 2 and 3 illustrate the manner in which the light is reflected and made to flicker according to the sound surface. A cross-section of the groove is shown in Fig. 2, the arrow line 16 illustrating the path of light entering the groove and the arrow line 9 indicating the path of the reflected light from the groove to the microscope 10.

Fig. 3 illustrates the direction of the illuminating rays along the groove. Quite obviously, the section of the wave marked A will be comparatively dark since it is over the crest, while the section marked B will be highly illuminated and will therefore reflect rays into the microscope when this section of the groove or wave passes under the light source as the record rotates. The section marked C will be comparatively dark and the reflected light reduced to a minimum. In this way, the amount of light passing through the microscope and falling on the photo-electric cell is varied,-

and corresponds to the sounds recorded on the record.

The photo-electric cell produces a pulsating electrical current corresponding to the light received. This current when amplified. and applied to a loud speaker, produces sound in accordance with the impulse received. In this way, I reproduce the sound carried by a phonograph record to which the device is applied.

Many obvious advantages will readily suggest themselves and. a few of them will be here pointed out.

More faithful reproduction will be obtained than with the usual method of reproduction of phonograph records. since this usual method includes mechanical contact with the record groove by a needle carrying a stylus bar and diaphragm for acoustic production and by a needle carrying an armature for electric production. Each of these systems involves a needle or stylus with a mechanical load attached to its top end.

The needle and its load are quite clumsy when compared with the magnitude and velocity of the sound vibrations they are attempting to transmit. When it is considered that the reproduction of a 6.000 cycle wave involves starting this mechanical bulk in one direction, stopping it and then starting it in the other direction 6,000 times each second. we realize that we are requiring too much of such a system. Measurements sh ow that the amount of a- 6.000 cycle sound reproduced with mechanical means is almost. ncgligible.

In addition to the weight and elasticity of the mechanical contact system, there are other faults. It is known that a phonograph needle wears flat at the point as it travels through the groove and that this flat has a dimension of .0068 inches, measured along the groove. The dimension of a 5,000 cycle wave at a point half-way through the ordinary disc record is .006? inches from crest to crest, and it is much less near the end of the record. Obviously, the flatened needle cannot follow this wave, but merely bumps along from crest to crest reproducing the wave in a distorted shape and in a greatly reduced volume.

Aside from the consideration of quality reproduction, there are other faults of the mechanical system of reproducing sound, such as wear and tear on the record, needle scratch and surface noise. ,These mechanical faults in addition to their harmful efi'ect on reproducing, are a problem in manufacturing the disc, and although this problem has been fairly well solved, it would be capable of a more satisfactory solution, should the element of wear be removed. As now manufactured, the disc must have two essential virtues, namely, wearing quality and smoothness of surface. \Vith the necessity "for the first mentioned virtue removed, greater freedom is allowed in formulating the record material wit-h an object of securing a smoother surface.

Having thus described the. invention, What is claimed is v 1. In a machine for reproducing sound, in combination, a sound record, means for throwing a beam of light on to said record, a microscope positioned to receive reflected light rays from a portion of the record, a light sensitive cell disposed beyond the eyepiece of said microscope, an amplifier, a circuit to said amplifier adapted to be closed when light is directed against said cell, and a loud speaker operated by said amplifier.

2. The combination as in claim 1, including a casing enclosing the cell and the eye piece of the microscope.

3. In combination with a body having a record groove therein, means for throwing a beam of light into said record groove, means for intercepting light rays reflected from said groove, a light sensitive cell, and said light ray intercepting means directing the intercepted light rays on to said light sensitive cell.

4. In a sound reproducing device to reproduce sound, a grooved record, a light source to cast light upon the record and a light sensitive element toreceive light reflected from the record.

5. The method of reproducing consisting in casting light rays on a sound record having a groove, collecting light rays reflected from the groove of the record, passing said collected light rays through a light sensitive cell and maintaining the collecting means in close proximity to the record surface.

sensitive element arranged to receive light from said lens system.

8. A record reproducing means comprising means to cast light onto a grooved record to be reproduced and means to direct light reflected from said record onto a photoelectric cell.

Signed at New York, in the county and State of New York, this 17th day of May,

REGINALD T. FRIEBUS. 

